A User's Guide to the Polygraph Exam

There are many examples throughout history of authorities attempting to detect deception. One of my favorites is that of certain priests in India circa 1500 B.C. A donkey's tail was covered with carbon residue from an oil lamp and placed in a dark room. The suspects were sent into the room and told that pulling the "magic" donkey's tail would reveal the liar. When the suspects came out, the priests examined their hands. Those with clean hands had not touched the donkey's tail. It was assumed that this was due to their fear of their guilt being discovered, proving they were liars. A nice theory with some psychological validity, but what if the guilty man had grabbed the donkey's tail to keep from falling in the dark or an innocent man simply couldn't find the tail in the dark? This probably would not have saved the innocent man – the test was just too convenient for the authorities.

In 1915 a Harvard professor named William Moulton Marston developed an instrument he termed a lie detector; it was a prototype polygraph based on blood pressure measurement alone. Four other men, John Larson, Leonarde Keeler, John Reid, and Fred Inbau, over decades, further developed the polygraph machine and the accompanying interrogation techniques into the modern polygraph test. Mr. Marston is not well known for his part in the development of the polygraph. But he did achieve fame in another area. He was the creator of the comic book character Wonder Woman who had a magic lasso that, when wound around a person, would force him to tell only the truth. As you will see there have been times when the magic lasso would have been preferable to the polygraph machine.

The polygraph is not a "lie detector." It is actually a "physiological reaction detector." It can accurately measure: (1) cardio response, in terms of blood pressure variations, heartbeat, and pulse wave; (2) skin resistance, which is affected by the amount of perspiration; and (3) rate of breathing.

All these measurements are affected by human emotion. There are, however, no scientific means of determining which emotion is affecting these measurements at any particular time. To the polygraph machine, fears, anger, anxiety, embarrassment, feelings of guilt are all the same, in varying degrees of intensity. Note that innocent but emotionally-excited people have failed polygraph exams miserably while some serial killers, with no feelings of remorse, have passed with barely a quiver of the polygraph's needles. The presumption and pronouncement of deception – indicating guilt – comes entirely from the interpretation of the polygraph examiner.

The polygraph exam when administered by a qualified, experienced, well-intentioned interrogator can be one useful tool, among many others, in focusing an investigation. It should never be any more than that.

In an ideal world, only experienced interrogators could become polygraph examiners. As it is there are competent examiners and there are pre-employment polygraph examiners who have no investigative or interrogation experience and only 80 hours of polygraph training. (Most states require a barber to have 1,000 hours of training.) The problems arise when authorities use it as a convenient magic lamp.

The polygraph exam is touted as a reliable scientific test. This simply isn't so. The Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP – whose members are all scientists) in the August 2001 of the committees' magazine, Skeptical Inquirer, did its own study of the polygraph exam. Its conclusions can be summed up in these quotes:

"The polygraph is a ruse, carefully constructed as a tool of intimidation, and used as an excuse to conduct an illegal inquisition under psychologically and physically unpleasant circumstances."

"[T]he polygrapher tries to persuade the unwitting subject that their measurements indicate when a lie is being told. The subject, nervously strapped in a chair, is often convinced by the aura surrounding this cheap parlor trick, and is then putty in the hands of the polygrapher, who launches into an intrusive, illegal, and wide-ranging inquisition. The subject is told, from time to time, that the machine is indicating 'deception' [it isn't, of course], and he is urged to 'clarify' his answers, by providing more and more personal information. At some point [it's completely arbitrary and up to the judgment of the polygrapher], the test is stopped and the polygrapher renders a subjective assessment of 'deceptive response.'"

Most courts do not allow polygraph exams to be introduced as evidence for several reasons. At their core is an unspoken reason (though well known to law enforcement and lawyers) that would torpedo the profitable and convenient polygraph industry. If the polygraph examiner is so inclined he can affect the readings of the polygraph machine to suit whatever interpretation he wishes to reach.

Why would any examiner wish to affect the polygraph results and by what method? The examiner and/or his bosses may have an agenda other than the truth and there are many ways this can be done.

There is a long history of abuse of the polygraph. Cases where people were subjected to hours of "third-degree" type interrogation and then immediately given a polygraph exam when their fear and anxiety were at their peak. Cases where shouts, threats, lies, and loud noises intimidated the subject during key questions in the exam.

Surely, you say, even if you fail a polygraph there is other evidence to consider. There may very well be other evidence if the authorities continue to look for it. A "deceptive" polygraph may stop the investigation with you. Many people have been convicted on circumstantial evidence alone and cleared by DNA evidence many [often 10 to 20] years later. A polygraph is a one-sided sword. If you fail, the investigation can stop with you. If you pass, you can not use it in court as a defense and it doesn't guarantee you won't be investigated and charged anyway. Surely the appeals system can undo an injustice? Consider that U.S. Supreme Court Justice Antonin Scalia has stated in a legal opinion that "... evidence of innocence is an insufficient cause for the reversal of a conviction." His position is that as long as no rules of procedure were violated and the evidence of innocence is not absolute, such reversals would cause a massive backlog in the courts and extreme inconvenience to the justice system. Once the justice system has invested in pursuing someone's guilt, it is reluctant to deflect that course.

A novice examiner who wishes to please his bosses (police, prosecutors, corporate bosses, etc) and demonstrate his ability to detect deception can even inadvertently taint an exam. My first experience with the polygraph was as a security officer, 30 years ago, at a large industrial plant. My rounds took an hour and 30 minutes to complete. One morning I found that an office had been broken into and valuable items had been stolen. I reported it to upper management and the police. A few days later I was asked by my boss to take a polygraph exam. At the time my knowledge of polygraph exams was no more than that of the average person. I agreed with no reservations or precautions. After the exam, my boss asked the examiner for the results in my presence. The examiner stated that I didn't lie directly when asked if I committed the burglary. But, he quickly added with the enthusiasm of a cat pouncing on a mouse, that the exam indicated that I had "guilty knowledge" of the crime. They both looked at me expectantly.

At that time those exam results would have been enough to get me fired and blackballed within the security community. I replied, "Of course I have knowledge of the crime. I discovered it first, examined the scene, reported it, and wrote a report that included an interview with the office's occupant to create an inventory of the stolen items." Fortunately, they were not yet deeply invested in me being the guilty party.

It is paradoxical, and hypocritical, that an exam to detect deception would depend heavily on deception in its execution. It is legally established that the police can lie to a suspect during an interrogation. Unofficially, polygraphers can and will do the same (unless they are police officers, then it is official lying).

A once common practice was the "Stim Test." The examiner would show the subject several playing cards at the start of an exam. The subject was asked to take one, look at it, and place it back into the deck. The subject would be instructed to answer "no" to every question; then the examiner would show the subject the cards one at a time, asking if that was the card. The idea: the card the subject picked would be the same card that the polygraph would detect as a lie. The examiner would tell the subject which card he picked to show the power of the polygraph. Sounds fair, right? It might have been if the cards weren't marked so the examiner was always aware of which card was picked by the subject. This was justified by the idea that this demonstration would encourage [read intimidate] the subject to tell the truth. No polygraph exam subject is allowed to watch the polygraph needles because this might affect his responses. It could be said that this would also interfere with the polygraphers' deception. To be fair, not all polygraphers approved of this method at the time but it is not banned.

Does this mean that you should never agree to a polygraph exam? Unfortunately, the polygraph exam has become so pervasive in our culture, especially in pre-employment screening, that that choice isn't always practical or possible. What I can do is give you some advice on how to protect yourself from a poor examiner.

First, you never take a polygraph exam without the advice and presence of a lawyer. As this is not always possible (again, especially in pre-employment screening) either, we will cover precautions with and without an attorney.

Second, always insist on knowing the qualifications of the examiner you will have. You may get a lot of resistance to this. When I was asked to take my second polygraph exam, some years later, I was a little smarter. When the polygraph examiner was offended and refused to reveal his qualifications, I refused to take the test. When my boss, the head of the detective agency, called me on the carpet for walking out on the test, I began to question him. If his daughter needed surgery would he just accept whatever surgeon was free right then? Or, would he research every bit of training and experience of all the surgeons available before choosing one? He agreed that I had a valid point. I was sent back to see the head of the polygraph agency. He showed me his excellent qualifications and assured me the examiner I had seen had his approval. However, he would not force the other examiner to display his qualifications to me. I said I would let them examine me only if the head of the polygraph agency did it, as I was satisfied with his experience. He declined. I did the same. Since my employer directed a lot of business to the polygraph company I got it my way in the end.

Now this will not guarantee that the polygraph exam will go your way if you are innocent. Remember that the best qualified polygraphers of each era were the same ones who developed the deceitful and faulty interrogation techniques. However, the most experienced examiners have more to lose than do those who are still learning, if they should be proved wrong later. This precaution will even the odds just a bit.

Thirdly, you will get incredible resistance to this next precaution but you need to persevere. It is standard practice in polygraph exams to ask innocuous "control" questions and for deliberate lies to certain questions as a basis for analyzing the final results. This sounds good but again, the examiner can never really be certain just what emotional reaction the polygraph machine is measuring.

The last time I was asked to take a polygraph it was in connection to a serious crime. This time I had done my research on polygraphs and was better prepared. I decided to use my own variation of the "Stim Test." I insisted the examiner ask me five questions I could prove the answers for that he could not know. I wanted the questions asked twice. One time I would answer no to all of them, the next time I would answer yes to all of them. You'll have to come up with you own questions, of course, but as an example I'll tell you mine.

Was your military service number B552478? It was not.

Was your mother's middle name Hazel? It was.

Was your first pet dog named Skippy? It was not. I still had labeled pictures.

Was your father's boyhood nickname "Butch"? I had no idea what the answer was. My father abandoned us when I was a 1-year-old. I just thought it would be interesting.

Do you have three dollar bills, a five-dollar bill, a $10 bill, and three nickels in your pockets? I did. I also had a $50 bill, two dimes, and three pennies in there. Again, I thought it would be interesting to see the result.

Everyone involved was outraged; the private detectives I worked for at the time, the police, and especially the polygrapher. I stated that I was going to be held accountable, one way or another, for the polygrapher's ability to accurately detect deception. Could they give me one good reason why I shouldn't be allowed to hold him accountable for the same? They couldn't of course. The polygrapher refused to be put to the test. Efforts were made to find a polygrapher who would agree to my conditions. Out of the dozen or more available polygraphers in the county not a single one would agree. Luckily the guilty party shortly came to light.

I was not protected by my defiance. I was not protected by my cleverness. I was protected because the polygraphers's feared an objective test of their ability to detect deception accurately during an exam. To be realistic, this approach will probably keep you from being hired in a pre-employment screening. It is more fitting in a case of criminal accusation.

You've hired an attorney, you're satisfied that the polygrapher is highly qualified and skilled, you've made your "Stim Test" request (most probably refused, but let's continue anyway), you've done your research, and you're fully prepared to take the exam. Well, not quite yet. There is one more way for the polygrapher to influence the polygraph readings that I know of. It is a subtle adaptation of psychological intimidation interrogation techniques.

Let's say your son (a first grader) is in a clumsy phase of his physical development. He shows up at school with an unusual number of bruises. In good conscience this is reported to authorities. You have been questioned by the police. You are innocent, but are still a suspect. The police offer you the opportunity to take a polygraph exam. You've conferred with your attorney and he advises that this kind of thing can get out of hand and recommends, presuming that you're innocent, that taking the exam is a way to settle it quickly. You made your concerns known to your attorney and the above precautions have been met. In between the "control" questions, relevant questions, and requested deliberate lies you may get questions like the following after being instructed to answer them only "yes" or "no."

Have you ever hit your son?

Have you ever made your son cry?

Has your son ever made you lose your temper?

Has your son ever been angry with you after you have disciplined him?

There will be more questions like this, but you get the idea. After all the questions are asked the polygrapher tells you there will be a break, then he will ask you the same questions again. Now I want you to walk away from this article and sit in an uncomfortable chair and do nothing for 20 minutes but try to not think about these questions. Seriously, go on now.

Time's up? Okay, could you not think about these questions? Of course not. Let me now provide some interpretation for you. Let's say you're a normal father in a normal household and during the test you were relaxed and thinking clearly. If so, you answered "yes" to those questions. Oops! The polygrapher, if so inclined, can tell the police there is "probable cause" to keep investigating you no matter what the results of the relevant questions were.

Let's now say you were focused on the charges of abuse (more likely) and you answered "no" to all the questions. Let me detect your thoughts during the break, one question at a time.

Have you ever hit your child? Well I have spanked him. That time he ran out into the street. Hard, too.

Have your ever made your son cry? He did cry when he was little and I wouldn't let him drink bleach. He cried when I wouldn't let him go to Girl Scout camp with his big sister. Oh yeah and the time he ran into the street.

Has your son ever made you lose your temper? Let me see. When he spilled hot chocolate on the new shag carpet. When he broke the Christmas ornament that I made when I was in first grade. When he cut his sisters' hair while she was asleep. And that time he ran into the street.

Has your son ever been angry with you after you have disciplined him? Yes, every time, especially that time he ran into the street. He's 6 years old!

Get the idea? You'll notice the key word in these questions is "ever."

Now the polygrapher comes back to ask the questions again. You're ready. You can get it right this time. You're a little anxious, but you can explain it. The examiner begins to ask the same questions, but not in the same order. Now you're a little more thrown off balance. If you decide to answer the "ever" questions "no" again your current state of anxiety will be reflected during the relevant questions. Even if it isn't you have strengthened the "probable cause" for a continued investigation. Let's say, this time, you answered the "ever" questions "yes" (if the examiner was not inclined to influence the polygraph readings, he would not be asking these kinds of questions). The examiner will ask you why you did this. You reply that after thinking about it you wanted to correct those answers. He will ask if there is any thing else you would like to correct now that you're thinking clearer about it. You'll say "no." He'll ask, are you sure, several times more during this part of the exam. There is more.

After asking all the questions, the examiner tells you to take another break (actually he is taking a break to compare the two sets of results while you're left to sweat some more) and then he will ask the questions one final time. Now you have time to realize that the examiner can honestly say you either lied during the first exam or the second. It must be one of them, right? Are you really sure you answered the other questions honestly? There are innumerable variations of this method. The insidious thing about this method is, once it gets rolling, the more you become aware of what's happening the worse it becomes for you. Now, assess the state of mind you think you would be in by the time the third set of questions is asked. What kind of reactions do you think the polygraph machine will be recording when you are asked the relevant questions the third time? Which set of reactions do you think will be interpreted by the examiner?

All is not lost though. Add the following precautions to the others.

Insist that you will not answer any questions twice, excepting your reversed "Stim Test."

Insist that you will only answer innocuous "control" questions, requested deliberate lie, and relevant, time and place specific questions. You will not answer any "fishing" or "somewhere in the ballpark" questions. If these kinds of questions are asked during the exam anyway, just don't answer them. Let the examiner try to justify asking them later.

Let me make this additional point. A polygraph exam is not an opportunity. A polygraph exam is not a formality. A polygraph exam is an assault. All the physiological and psychological stress reactions generated by the body during a physical assault can be mirrored during a polygraph exam, varying only, perhaps, by degree of intensity. The whole concept of the polygraph exam is based on this.

Finally, remember that every situation is different and that you (ideally with the advice of counsel) are the best judge of how to proceed or not proceed. I hope this article will forewarn and forearm you enough to guide you and help even up the odds in an often-rigged game. Do your own research. There may be a situation just like yours out there. Unfortunately, it can be a crapshoot with infinite variables and the only sure way of winning is to avoid playing.

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With the purpose of writing about true crime in an authoritative, fact-based manner, veteran journalists J. J. Maloney and J. Patrick O’Connor launched Crime Magazine in November of 1998. Their goal was to cover all aspects of true crime: Read More